Printhead structure in an image recording device

Abstract

An image recording apparatus includes a toner particle source for delivering charged toner particles to an image receiving medium. The image recording apparatus further includes a printhead structure arranged between the toner particle source and the image receiving medium to modulate a transport of toner particles from the particle source to the image receiving medium. The printhead structure includes a substrate of electrically insulating material having a first surface facing the toner particle source and a second surface facing the image receiving member. A first cover layer of electrically insulating material is arranged on the first surface of the substrate. A plurality of apertures are arranged through the printhead structure. A first printed circuit including control electrodes is arranged between the substrate and the first cover layer to control the transport of toner through the apertures and a spacer layer of wear-resistant material at least partially coats the first cover layer to space the first cover layer from the toner particles on the particle source.

What is claimed is: 
     
       1. A printhead structure in an image recording apparatus which includes a toner particle source for delivering charged toner particles to an image receiving medium, said printhead structure being arranged between the toner particle source and the image receiving medium to modulate a transport of toner particles from the particle source to the image receiving medium, said printhead structure comprising: a substrate of electrically insulating material having a first surface abutting the toner particle source and a second surface facing the image receiving member;   a first cover layer of electrically insulating material arranged on said first surface of the substrate;   a plurality of apertures arranged in depression areas through the printhead structure;   a first printed circuit including control electrodes arranged between said substrate and said first cover layer to control the transport of toner through the apertures; and   a spacer layer of wear-resistant material at least partially coating the first cover layer and in contact with the toner particles to space the first cover layer from the toner particles on the toner particle source.   
     
     
       2. The printhead structure of claim 1, wherein the spacer layer is a film of diamond-like nature. 
     
     
       3. The printhead structure of claim 2, wherein the spacer layer comprises amorphous carbon. 
     
     
       4. The printhead structure of claim 2, wherein the spacer layer comprises a film of hydrogenated amorphous carbon having from about 1 to about 60 weight percent of hydrogen. 
     
     
       5. The printhead structure of claim 2, wherein the spacer layer comprises a film of halogenated amorphous carbon wherein the halogen is present in an effective amount of from about 1 to about 40 weight percent. 
     
     
       6. The printhead structure of claim 2, wherein the spacer layer comprises a film of halogenated amorphous carbon wherein the halogen is present in an effective amount of from about 1 to about 20 weight percent. 
     
     
       7. The printhead structure of claim 2, wherein the spacer layer comprises a film of fluorinated amorphous carbon having from about 1 to about 40 weight percent of fluorine. 
     
     
       8. The printhead structure of claim 2, wherein the spacer layer comprises a film of fluorinated amorphous carbon having from about 1 to about 20 weight percent of fluorine. 
     
     
       9. The printhead structure of claim 2, wherein the spacer layer has a thickness in a range from about 50 nanometers to about 200 nanometers. 
     
     
       10. The printhead structure of claim 2, wherein the spacer layer has a thickness in a range from about 100 nanometers to about 150 nanometers. 
     
     
       11. The printhead structure of claim 1, wherein the first cover layer has an initial thickness facing the particle source, said first cover layer having depression areas arranged in said initial thickness. 
     
     
       12. The printhead structure of claim 11, wherein the apertures through the printhead structure are arranged in the depression areas, the part of the apertures facing the particle source being sunken in said initial thickness of the first cover layer. 
     
     
       13. The printhead structure of claim 11, wherein the depression areas extend at a predetermined depth in the initial thickness of the first cover layer, wherein each aperture through the printhead structure is arranged in a corresponding depression area, the part of the apertures facing the particle source being sunken a distance in the initial thickness of the first cover layer. 
     
     
       14. The printhead structure of claim 11, wherein the toner particle source comprises a rotating toner particle carrier having a rotation axis extending in a first direction and an outer surface coated with a toner particle layer, the spacer layer being tensioned against said outer surface of the toner particle carrier, whereby said toner particle layer is brought in contact with the spacer layer over a predetermined contact surface of the spacer layer, and the apertures through the printhead structure are arranged in depression areas, the part of the apertures facing the particle source being thereby spaced from said toner particle layer. 
     
     
       15. The printhead structure of claim 14, wherein the apertures are arranged in at least two parallel rows extending in said first direction. 
     
     
       16. The printhead structure of claim 14, wherein said contact surface of the spacer layer at least partially surrounds each of said depression areas. 
     
     
       17. The printhead structure of claim 14, wherein the depression areas are arranged in at least two parallel rows extending in said first direction, and said contact surface of the spacer layer extends between the depression areas of each row. 
     
     
       18. The printhead structure of claim 14, wherein the depression areas are arranged in at least two parallel rows extending in said first direction, and said contact surface of the spacer layer extends on a upstream side of each depression area with respect to the rotation of the toner particle carrier. 
     
     
       19. The printhead structure of claim 14, wherein said contact surface of the spacer layer extends between the depression areas of each row. 
     
     
       20. The printhead structure of claim 14, wherein the depression areas are arranged in at least two parallel rows extending in said first direction, and the depression areas have substantially the same extension as the apertures in said first direction. 
     
     
       21. The printhead structure of claim 14, wherein each aperture is arranged in a corresponding depression area, the depression areas having substantially the same extension as the apertures in said first direction, each depression area extending on the downstream side of a corresponding aperture with respect to the rotation of the toner particle carrier, and said contact surface of the spacer layer extending on a upstream side of each aperture with respect to the rotation of the toner particle carrier. 
     
     
       22. The printhead structure of claim 21, wherein each depression area extends at a predetermined depth with respect to said contact surface of the spacer layer, said predetermined depth being substantially constant in a second direction, said second direction being perpendicular to said first direction. 
     
     
       23. The printhead structure of claim 21, wherein each depression area extends at a predetermined depth with respect to said contact surface of the spacer layer, and said predetermined depth decreases in a second direction, perpendicular to said first direction, from a maximal value in the vicinity of the aperture. 
     
     
       24. The printhead structure of claim 21, wherein the depression areas are similarly spaced, parallel tracks extending in a second direction, perpendicular to said first direction, on a downstream side of the apertures with respect to the rotation of the toner particle carrier, the contact surface of the spacer layer extending between said tracks. 
     
     
       25. The printhead structure of claim 1, wherein a portion of each control electrode of the first printed circuit at least partially surrounds a corresponding aperture, each control electrode being connected to a variable voltage source supplying control voltage pulses which permit or restrict the transport of toner particles from the toner particle source through the corresponding aperture in accordance with an image information. 
     
     
       26. The printhead structure of claim 25, wherein the first printed circuit further comprises at least one shield electrode extending between said control electrodes, said shield electrode is connected to a shield voltage source supplying a shield potential to electrostatically shield said control voltage pulses from one another, thereby preventing interference between adjacent control electrodes. 
     
     
       27. The printhead structure of claim 25, wherein the apertures are arranged in at least two parallel rows extending in a first direction, the portion of the control electrodes surrounding the apertures is smaller in said first direction than in a second direction, the second direction being perpendicular to said first direction. 
     
     
       28. The printhead structure of claim 26, wherein the apertures are arranged in at least two parallel rows extending in a first direction, and the shield electrodes extend substantially in said first direction between said aperture rows. 
     
     
       29. The printhead structure of claim 26, wherein the apertures are arranged in at least two parallel rows extending in a first direction, and the shield electrodes extend substantially in said first direction between said aperture rows and in a second direction between the apertures of each aperture row. 
     
     
       30. The printhead structure of claim 1, further comprising: a second cover layer arranged on said second surface of the substrate, said second cover layer having a bottom surface facing the image receiving medium; and   a second printed circuit comprising segmented deflection electrodes arranged between the substrate and said second cover layer.   
     
     
       31. The printhead structure of claim 30, wherein each segmented deflection electrode has a first deflection segment and a second deflection segment, the segmented deflection electrodes being connected to deflection control means for sequentially producing potential differences between said first and second deflection segments, thereby deflecting toner particles passing through the apertures toward predetermined pixel locations on the image receiving medium. 
     
     
       32. The printhead structure of claim 30, wherein the printhead structure cooperates with an image receiving medium moving in a predetermined direction relative to the printhead structure, in which each aperture has a central axis through the printhead structure, and each segmented deflection electrode has a first deflection segment and a second deflection segment disposed symmetrically about said central axis of a corresponding aperture. 
     
     
       33. The printhead structure of claim 32, wherein each segmented deflection electrode has a first deflection segment and a second deflection segment disposed on each side of a deflection axis extending through said central axis of a corresponding aperture at a predetermined deflection angle to said predetermined direction of the image receiving medium. 
     
     
       34. The printhead structure of claim 33, wherein said deflection angle is in a range of about 10° to about 40°. 
     
     
       35. The printhead structure of claim 33, wherein said deflection angle is in a range of about 18° to 27°. 
     
     
       36. The printhead structure of claim 30, further comprising a layer of semi-conductive material coated on at least a part of said bottom surface of said second cover layer. 
     
     
       37. A method for producing a printhead structure for an image recording apparatus which includes a toner particle source for delivering charged toner particles in a position adjacent to an image receiving medium, wherein the printhead structure is arranged between the toner particle source and the image receiving medium to modulate a transport of toner particles from the toner particle source to the image receiving medium, the method comprising: providing a substrate of electrically insulating material having a first surface abutting the toner particle source and a second surface;   forming a plurality of apertures in depression areas through the printhead structure;   forming a printed circuit on said substrate proximate to said first surface, said printed circuit comprising a plurality of control electrodes being formed around said apertures;   forming a first cover layer of electrically insulating material on said substrate over said printed circuit, said first cover layer of electrically insulating material having a top surface which faces away from said substrate;   coating at least a portion of said top surface of said first cover layer of electrically insulating material with a spacer layer of wear-resistant material the spacer layer contacting the toner particles to space said top surface from the toner particles when said printhead structure is positioned proximate to the toner particle source.   
     
     
       38. A printhead structure in an image recording apparatus which includes a toner particle source for delivering charged toner particles to an image receiving medium, said printhead structure comprising: a control electrode array having a first surface abutting the toner particle source; and   a spacer layer of wear-resistant material at least partially coating the first surface of the control electrode array and in contact with the toner particles to space the control electrode array from the toner particles on the toner particle source.